1. Field of the Invention
The present invention relates to an electric connection box for preventing wear of heavy electric component terminals, such as a relay, and busbar terminals and trunk terminals in the electric connection box, due to movement of the electric component with vibration.
2. Description of the Related Art
FIG. 7 shows an embodiment of a conventional electric connection box (JP, 2000-331759,A).
The electric connection box 71 includes a relay 72, as an electric component, having relay male terminals 73, conductive trunk terminals 76 disposed between an upper cover 74 and a lower cover 75, and busbar boards 77 having busbars 78 with busbar male terminals 79. The relay male terminals 73 are connected with the busbar male terminals 79 through the trunk terminals 76.
The relay 72 turns on and off a main circuit with excitation of a coil in the relay against the busbars 78. The busbars 78 are strip-shaped conductive circuit bodies and have the busbar male terminals 79, which are formed by bending vertically end portions of the busbars 78. The upper cover 74 has a relay attachment portion 80 and a trunk terminal receiving room 81. A lower face of the relay 72 abuts to an upper face of the relay attachment portion 80. The lower cover 75 is fixed to the upper cover 74 and receives a plurality of the busbar boards 77 which are laminated each other.
Each busbar board 77 has the plurality of the busbars 78 separated by insulation substrates made of a synthetic resin. The trunk terminals 76 each have a pair of resilient contact pieces at an upper and lower portion of the vertical substrate. The relay male terminals 73 and busbar male terminals 79 are inserted between the substrate and the resilient contact pieces.
FIGS. 8 and 9 show another embodiment of a conventional electric connection box.
An electric connection box 82 includes an upper cover 83, a lower cover 3, guide walls 51, and flexible locking frames 53, which extend outwardly from the upper cover 83. The guide walls 51 have an L-shape and are arranged to be fitted with corners of the relay 6. The lower portions of the four corners of the relay 6 are guided by the guide walls 51 and locking protrusions 27 of the relay 6 are engaged with the locking frames 53. The relay 6 is usually for a high current and high voltage use.
The upper cover 83 and lower cover 3 are fitted together with flexible side locking frames 10 and side locking protrusions 11. The lower cover 3 has brackets 85 for fixing the lower cover 3 to a vehicle body. A middle plate 47 made of a synthetic resin is disposed above the lower cover 3. The busbars 86 are arranged on the middle plate 47 and between the middle plate 47 and the lower cover 3. Busbar male terminals 49 upstanding from the busbars 86 are connected to the relay male terminals 30 through the trunk terminals 48.
The trunk terminals 48 have resilient contact pieces 63 at middle portions thereof and contact walls 68, 69 opposed to the resilient contact pieces 63. The busbar male terminals 49 and relay male terminals 30 are connected together through the common resilient contact pieces 63.
In the conventional electric connection box 82 of FIGS. 8 and 9, as shown in FIG. 10, spaces S3 and S4 are formed in respective directions of X and Y between the guide walls 51 and the relay 6 when the relay 6 is attached to the relay attachment portion 84. Vibration of a vehicle at running or stopping moves the heavy relay 6 in the directions of X and Y, back and forth and leftward and rightward. This movement causes wears of the relay male terminals 30 and trunk terminals 48 and bends the resilient contact pieces 63 of the trunk terminals 48. As a result of that, the contact pressure between the relay male terminals 30 and the busbar male terminals 49 is reduced.
As shown in FIG. 11, the guide walls 51 are tapered for easy molding. An upper space S5 is larger than a lower space S6. Accordingly, the relay 6 swings inside the guide walls 51 in a direction of C and the relay male terminals 30 swing in a direction D. This movement accelerates the wear of the relay male terminals 30 and the trunk terminals 48 and the bending of the resilient contact pieces 63.
As shown in FIG. 9, there are other spaces S2 and S7 in a direction of Z for locking between the locking protrusions 27 and the locking frames 53 and between the side locking frames 10 and the side locking protrusions 11. An upper wall of the upper cover 83 is deformed with the weight of the relay 6 or the depression force of attachment of the relay 6. The spaces S2, S7 and the deformation of the upper cover 83 change a distance of H2 between an upper face of the lower cover 3, which contacts with the busbars, and a lower face of the relay 6 and a distance of H3 between an upper face of the middle plate 47, which contacts with the busbars, and the lower face of the relay 6. The large changes of H2 and H3 cause the wear of the relay male terminals 30, trunk terminals 48 and busbar male terminals 49.
When a large and heavy fusible link is utilized instead of the relay 6 and the relay male terminals 30 are directly connected to the busbar male terminals 86, not shown, without the trunk terminals 48, the same problems, such as the wear and bending, occur.